284 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 7 



the inner margin. This gentle slope breaks abruptly to 22° at its 

 outer margin. The profile from the edge of the shelf to the normal 

 ocean jQoor at 2,600 fathoms is, as might be expected, concave upward. 

 From an average of 22° at the top it gradually decreases in steepness 

 until it forms a smooth tangent with the ocean floor at the bottom. 



Figure 3. — Fathometer recorder trace of a typical guyot. Note irregularities on 

 lower slopes with considerable thickening (lengthening) of the echo trace. 

 These indicate steep slopes to the side (parallel to ship's course) and necessitate 

 an adjustment to obtain the approximate depth immediately beneath the ship. 

 The adjustment has been made in figure 4. 



Figures 3 and 4 are reproductions of the sounding traverse across 

 the guyot. 



Guyots vary widely in size. One a few miles northeast of Eniwetok 

 has a flat summit only a couple of miles across (latitude 11°45' N., 

 longitude 162°55' E.) ; whereas one some distance farther northeast 

 apparently has a flat upper surface 35 miles wide and has a diameter 

 of 60 miles at its base (latitude 14° N., longitude 167°30' E.). In 

 general they appear to be circular or oval in. plan. No correlation has 



